With miniaturization of semiconductor devices such as a large-scale integrated circuit (hereinafter referred to as an LSI), the technical difficulty of a processing technique of controlling leakage current interference between transistor elements has been increasing. In general, separation between elements of an LSI is performed using a method of forming a void, such as a groove or a hole, between elements to be separated in a substrate, such as a silicon substrate formed of, for example, silicon (Si), and depositing an insulating material in the void. In many cases, an oxide film is used as the insulating material. For example, a silicon oxide (SiO2) film may be used as the oxide film. The silicon oxide film is formed by native oxidation of a silicon substrate itself or chemical vapor deposition (hereinafter also referred to as CVD). As an example, Patent document 1 discloses an example of a method of forming an insulating film using CVD.
Due to recent miniaturization of semiconductor devices, a void is formed on a substrate to have a deep structure in a longitudinal direction or to have a narrow, fine structure in a transverse direction. The void having the fine structure is filled using CVD to form an oxide film on the substrate. However, formation of a film in the void having the fine structure using CVD is reaching its technical limit.
Thus, a filling method using an oxide having fluidity, that is, a method of coating a dielectric material (spin on dielectric, hereinafter, also referred to as an SOD technique), has attracted attention. In the SOD technique, a coating dielectric material containing an inorganic or organic element called spin on glass (SOG) is used. A filling method using the coating dielectric material was adopted for a process of fabricating an LSI before the advent of the above-described technique of forming an oxide film on a substrate using CVD.
In the above-described SOD technique, a processing dimension ranges from about 0.35 μm to about 1.0 μm. In comparison, recent semiconductor devices represented as an LSI, a dynamic random access memory (DRAM), and a flash memory have the minimum processing dimension of less than 50 nm. For this reason, there may be some cases in which it is difficult to form an oxide film on a substrate having a fine structure using an SOD technique while maintaining the quality of an insulating film.